Peroxide-crosslinkable compositions and processes for their manufacture

Abstract

A peroxide-crosslinkable composition comprising: (A) A peroxide-crosslinkable polymer, e.g., a polyethylene; (B) A nitrogenous base, e.g., a low molecular weight, or low melting, or liquid nitrogenous base such as triallyl cyanurate (TAC); and (C) One or more antioxidants (AO), e.g., distearylthiodipropionate (DSTDP). The composition is useful in the manufacture of insulation sheaths for high and extra high voltage wire and cable.

What is claimed is: 
     
       1. A peroxide-crosslinkable composition comprising:
 (A) a peroxide-crosslinkable polymer; 
 (B) a low molecular weight, or low melting, or liquid nitrogenous base at 0.0005 wt % to 0.01 wt %, based on the weight of the composition, the low molecular weight nitrogenous base having a molecular weight less than or equal to 1,400 g/mol and the low melting nitrogenous base having a melting temperature less than or equal to 95° C.; 
 (C) one or more antioxidants (AO); and 
 (D) optionally, a peroxide. 
 
     
     
       2. The composition of  claim 1  in which the base comprises triallyl cyanurate and/or N,N′-1,6-hexanediyl-bis-N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide and/or mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate. 
     
     
       3. The composition of  claim 1  in which the antioxidant comprises distearylthiodipropionate. 
     
     
       4. A process for making a peroxide-crosslinkable pellet, the process comprising the steps of:
 (1) forming a homogeneous melt of:
 (A) a peroxide-crosslinkable polymer; 
 (B) a low molecular weight, or low melting, or liquid nitrogenous base at 0.0005 wt % to 0.01 wt %, based on the weight of the pellet, the low molecular weight nitrogenous base having a molecular weight less than or equal to 1,400 g/mol and the low melting nitrogenous base having a melting temperature less than or equal to 95° C., and 
 (C) optionally, an antioxidant (AO); 
 
 (2) passing the homogeneous melt of (1) through a filter with a mesh size of less than 100; and 
 (3) forming pellets from the filtered homogeneous melt of (2). 
 
     
     
       5. The process of  claim 4  comprising the further step of impregnating the pellets with a peroxide. 
     
     
       6. A process for making a peroxide-crosslinkable pellet, the process comprising the steps of:
 (1) forming a melt of a peroxide-crosslinkable polymer with AO; 
 (2) passing the melt of (1) through a filter with a mesh size of less than 100 μm; 
 (3) forming pellets from the filtered homogeneous melt of (2); and 
 (4) impregnating the pellets with a low molecular weight or liquid nitrogenous base, the low molecular weight nitrogenous base having a molecular weight less than or equal to 1,400 g/mol. 
 
     
     
       7. The process of  claim 6  in which the pellets are also impregnated with a peroxide. 
     
     
       8. A wire or cable comprising a sheath made from the composition of  claim 1 . 
     
     
       9. A wire or cable comprising a sheath made from a pellet made by the process of  claim 4 . 
     
     
       10. A wire or cable comprising a sheath made from a pellet made by the process of  claim 6 . 
     
     
       11. The composition of  claim 1  in which the base comprises the low molecular weight nitrogenous base or the low melting nitrogenous base, and the antioxidant comprises sulfur. 
     
     
       12. The composition of  claim 1  in which the base comprises triallyl cyanurate. 
     
     
       13. The composition of  claim 1  in which the base comprises N,N′-1,6-hexanediyl-bis-N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide. 
     
     
       14. The process of  claim 4 , wherein the filter has a mesh size of less than 50 μm. 
     
     
       15. The process of  claim 6 , wherein the filter has a mesh size of less than 50 μm.